Turkey: It was in our airspace without permission, we shot it down
Russia: It was in Syrian territory. This is a very serious incident.
Neither side are backing down an inch. The sort of rhetoric that comes before bigger incident.
CNN Turkey have released a radar track from the Turkish military that shows a couple of tracks clipping the edge of Turkish airspace. Either the Turkish military have some very loose rules of engagement or someone has a hair trigger and a point to prove.
Although it's dangerous to do this based on virtually no hard facts, surely it would have been better to make this a public complaint about the Russians rather than shoot first. (Caveated by me not knowing if there have been other incidents unreported and the Turks have just had enough or even knowing if the radar track is right.)